需求：伺服器不斷的接收返回資訊到客戶端中，客戶端可以不斷地額給伺服器傳送訊息，並可以接收到伺服器返回的訊息。這跟我們聊天一樣。

思路：1、伺服器端：1）建立ServerSocket和開啟監聽客戶端連線

                                       2）在迴圈中構建IO流，不斷的讀取客戶端傳送過來的資料。

            2、客戶端：1）建立Socket和伺服器連線通訊

                                   2）再迴圈中構建IO流，不斷的通過鍵盤輸入訊息傳送到伺服器中，在接收來自伺服器返回的訊息

伺服器端：

package server.cotrol;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server03 {
	public static void main(String[] args) {
		try {
			ServerSocket ss = new ServerSocket(8888);
			System.out.println("伺服器已啟動");
			Socket s = ss.accept();
			//構建IO流
			while(true){
				BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
				String mess = br.readLine();
				BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
				//為了證明是伺服器返回的資料，我對mess修改在傳送到客戶端
				String str = "伺服器>>"+mess+"\n";
				bw.write(str);
				bw.flush();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}
 

package client.cotrol;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.Scanner;

public class Client03 {
	public static void main(String[] args) {
		try {
			Socket s = new Socket("127.0.0.1",8888);
			System.out.println("客戶端IP:"+s.getLocalAddress()+"埠"+s.getPort());
			//構建IO流
			BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
			
			//建立鍵盤輸入：
			Scanner scanner = new Scanner(System.in);
			while(true){
				System.out.println("請輸入傳送訊息內容：");
				bw.write(scanner.nextLine()+"\n");
				bw.newLine();
				bw.flush();
				BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
				//讀取伺服器返回的訊息資料
				System.out.println(s.getInetAddress().getLocalHost()+":"+s.getPort()+">>"+br.readLine());
			}
			
			
		} catch (UnknownHostException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}
}